Effects of light perception on visual function recovery in patients with traumatic optic neuropathy

This study aimed to assess the impact of light perception presence or absence on visual function recovery in patients with traumatic optic neuropathy (TON). A retrospective analysis was conducted on the clinical data of 206 TON patients. Based on the presence or absence of light perception after injury, patients were categorized into a light perception group and a non-light perception group. A comparison was made between the two groups regarding visual acuity recovery before and after treatment. The non-light perception group comprised 63 patients, with a treatment effectiveness rate of 39.68%. The light perception group consisted of 143 patients, with a treatment effectiveness rate of 74.83%. The difference between the two groups was statistically significant (χ2 = 23.464, P < 0.01). Subgroup analysis indicated that surgical treatment appeared to be more effective than steroid hormone therapy for patients with light perception. Conversely, for patients without light perception, there was no significant difference in the effectiveness of the two methods. The total effectiveness rate of the light perception group was significantly higher than that of the non-light perception group, suggesting that patients with light perception before treatment experience better outcomes compared to those without light perception. Treatment choices should be individualized to ensure optimal results.


Statistical analysis
The data were analyzed using statistical software (SPSS version 26; IBM Corp., Armonk, NY, USA).Continuous variables were presented as mean ± standard deviation (X ± S).T-tests were used to compare means between two groups for continuous variables.Categorical variables were expressed as percentages (%), and the therapeutic effective rate between the two groups was compared using the chi-square test.A P value of less than 0.05 was considered statistically significant.

Baseline characteristics of patients
Table 1 provides a description of the clinical manifestations of the patients included in this study.All patients had unilateral optic nerve injuries, with 130 cases resulting from traffic accidents and 76 cases resulting from simple trauma such as falls or blows.Preoperative CT scans revealed varying degrees of orbital and cranial bone fractures in 156 patients, accounting for 75.7% of the total number of patients.Among the patients, 143 had light perception, and 63 had no light perception.In the light perception group, there were 93 males and 50 females, aged 18-69 years (mean age: 42.32 ± 12.18 years).Among them, 80 cases had injuries to the left eye, and 63 cases had injuries to the right eye.Of these, 57 cases visited the hospital within 24 h of the injury, 52 cases within 1-3 days, 28 cases within 4-7 days, and 6 cases more than 7 days after the injury.In the group without light perception, there were 36 males and 27 females, aged 21-64 years (mean age: 39.89 ± 11.01 years).Among them, 31 cases had injuries to the left eye, and 32 cases had injuries to the right eye.Of these, 37 cases visited the hospital within 24 h of the injury, 18 cases within 1-3 days, 7 cases within 4-7 days, and 1 case more than 7 days after the injury.There were no statistically significant differences in age, gender, or injured side between the two groups (P > 0.05).Attached list 1 showed each person's specific initial vision and change.

Comparison of therapeutic effects between non-light perception group and light perception group
The overall effective rate of the light perception group was significantly higher than that of non-light perception group, with a statistically significant difference (χ 2 = 23.464,P < 0.01, Table 2).

Subgroup analysis: Comparison of treatment methods on therapeutic effects
Among the patients in light perception group, 52 received surgical treatment and 91 received steroid treatment.The overall effective rate of the surgical treatment group was higher than that of the steroid treatment group, with a statistically significant difference (χ 2 = 8.066, P < 0.01, Table 3).Among the patients in non-light perception group, 40 received surgical treatment and 23 received steroid treatment.There was no statistically significant difference in the overall effective rate between two groups (χ 2 = 0.363, P = 0.55, Table 4).

Discussion
The optic nerve, comprised of retinal ganglion cell axons, is a specialized sensory nerve with a total length of approximately 40 mm 13 .Anatomically, it can be divided into four segments: the intraocular segment (about 1 mm), intraorbital segment (about 25 mm), intracanalicular segment (5-6 mm), and intracranial segment (10 mm).External impact on any segment of the optic nerve can lead to severe nerve damage.The intracanalicular segment, which is the most delicate and represents the site where the optic nerve enters the cranial cavity, exhibits the highest incidence of injury at 71.4% 14,15 .On one hand, trauma can transmit external forces to the optic nerve canal, resulting in damage to the optic nerve due to the vulnerability of the bony structures surrounding the canal, such as the root of the lesser wing of the sphenoid and the base of the anterior clinoid process.On the other hand, trauma can cause optic nerve swelling and necrosis through compression of the optic nerve and its nutrient vessels due to bone fragment displacement or bleeding [16][17][18] .As a component of the central nervous system, the optic nerve possesses limited regenerative ability, and once the process of neuronal apoptosis begins, it becomes challenging to halt, leading to the death of numerous ganglion cells 19,20 .While various eye diseases, such as optic neuritis, retinal detachment, and ischemic optic neuropathy, can result in optic nerve damage, TON is more frequently encountered by neurosurgeons, predominantly caused by car accidents, followed by falls, blows, and fights 21 .Among our group of cases, car accidents accounted for 130 cases (63.11%), falls for 32 cases (15.53%), blows and fights for 37 cases (17.96%), and other causes for 7 cases (3.4%).Optic nerve injury mechanisms in these patients can be categorized into two types: direct injury and indirect injury 22 .Direct injury often arises from violence directly impacting the outer edge of the orbit, while indirect injury frequently occurs due to optic nerve-related blood vessel spasm resulting from violence to the supraorbital margin and nasal bone 23,24 .
Following optic nerve injury, patients frequently present with clinical symptoms, such as visual field defects, impaired color vision, and potentially vision loss.In clinical practice, it is crucial to promptly identify and prioritize these symptoms, intervening early to provide treatment in order to salvage as many nerve cells as possible 25 .
Once diagnosed, immediate treatment is essential for optic nerve injuries.Currently, there is no standardized treatment protocol in clinical practice 26 .The main treatment methods include high-dose steroid pulse therapy and optic nerve decompression surgery, supplemented with diuretics, vasodilators, and drugs that improve microcirculation 27,28 .Conservative treatment often involves high-dose methylprednisolone pulse therapy.In our department, we typically administer 500 mg of methylprednisolone within 3-8 h of injury, followed by a 3-day pulse treatment with a dose adjustment to 300 mg.Steroids possess anti-inflammatory and antioxidant effects, reducing the formation of free radicals, alleviating edema reactions, and preventing vascular spasm.These properties inhibit nerve cell necrosis and protect the optic nerve 29 .Optic nerve decompression surgery involves surgically removing pressure on the optic nerve to facilitate self-repair.Surgical treatment is preferred for patients with noticeable bone fragments and hematomas compressing the optic nerve, which can include traditional transcranial optic nerve decompression surgery and intraorbital optic nerve decompression surgery 30,31 .Endoscopic optic nerve decompression surgery through the nasal cavity has also been utilized.Currently, there are no randomized controlled studies evaluating the therapeutic effects of different surgical techniques, so the primary criterion for selection remains the proficiency of the clinical physician 32 .Studies indicate that the combined effect of optic nerve decompression surgery and steroid therapy is superior to a single treatment plan, but more research is needed to substantiate this claim 33 .
In this study, there were 63 patients with no light perception after injury, yielding an effective treatment rate of 39.68%.Additionally, 143 patients had light perception after injury, with an effective treatment rate of 74.83%.The χ 2 value was 23.464, P < 0.01, demonstrating a statistically significant difference.These findings indicate that patients who retained light perception before treatment exhibited better treatment outcomes than those who did not.Patients without light perception, regardless of steroid or surgical treatment, are unlikely to experience significant vision improvement, with low degrees of improvement observed.Existing reports suggest that patients with residual vision or light perception may have intact or partially ischemic optic nerves, with a considerable number of surviving ganglion cells 34 .Conversely, patients with no light perception may have experienced severe or irreversible optic nerve transection or necrosis, with few to no surviving ganglion cells.Hence, vision restoration is possible in the former case, emphasizing the importance of timely intervention and treatment for vision recovery.However, the possibility of vision restoration is considerably lower in the latter scenario.
The selection of treatment options for TON has long been a subject of controversy 26 .Further subgroup analysis of our study reveals that for patients with residual light perception, surgical treatment may be more effective than pure steroid therapy.Conversely, for patients without light perception after injury, the effectiveness of the two treatment options does not differ significantly.Therefore, the choice of a specific treatment plan should be individualized.For patients with residual vision after injury, regardless of visual acuity level, early and timely treatment should be administered.Steroid therapy or surgical treatment should be selected based on the actual situation to maximize ganglion cell survival and provide potential for further visual recovery.We suggest that surgery should be performed as soon as possible for clear fracture fragments, or obvious hematoma in the optic canal, or obvious indications of optic nerve compression on CT.Hormone therapy alone cannot solve the problem of optic nerve compression, and hardly help improve the patient's optic nerve function.For patients without obvious optic nerve compression, whose vision did not improve after accepting high-dose hormone treatment for 3 days, or whose vision improved first but deteriorated during hormone reduction, we still recommended early surgical treatment.However, whether or not to undergo surgery ultimately depends on the actual experience of clinicians and the wishes of patients themselves.In cases where patients have no light perception after injury, the appropriate treatment method should be carefully chosen, taking into account the potential risks of optic nerve injury or necrosis associated with intervention.

Conclusion
Prompt diagnosis and treatment are crucial for patients with TON, regardless of the chosen treatment method.This is particularly important for patients who retain light perception after the injury, as early administration of appropriate treatment can help preserve more surviving ganglion cells and promote visual recovery. https://doi.org/10.1038/s41598-024-54324-1www.nature.com/scientificreports/

Table 1 .
Baseline characteristics of patients.

Table 2 .
Comparison of therapeutic effects between non-light perception group and light perception group.

Table 3 .
Comparison of treatment methods on light perception group.